Dynamo-electric machine



H. WEICIISEL. DYNAMO-ELECTRIC MACHINE.

APPLICATION FILED DEC- 17. I920.

Patented Apr. 4, 1922 INVENTOR ATTORNEY UNITED STATES PATENT 1 OFFICE.

HANS wnrcnsnr, on ST. LOUIS, MISSOURI, ASSIGNORTTO .WAGNER ELECTRICMANU- FACTURING COMPANY, or, sir, LOUIS, MISSOURI, A CORPORATIONorimssovnr.

DYNAMOQLLEUIJRIC MACHINE.

Specification of Letters Patent.

' Patented Apia 1,1922.

Application. filed Decemberil'i, 1920.= Serial No.. 431,325.

citizen ofGermany. residing the city of- Shliouis, State of Missouri,United States ofrAmerica, haveinvented a certaininew and usefulvDynamo-.l*llectric Machine, of

which the following issuclra full, clear, and exact description as willenable-any one skilled in theartto which? it appertains to make and usethe same, reference being had to the accompanying drawings. forming partof this specification.

My invention relates to dynamo electric machines, and particularly todirect current series motors designed to operate on very low voltagecircuits such as are, for instance, used on motor cars. Vhen suchmachines are required to develop very large turning efforts, they mustbe built to handle very large currents and when the c pacity of thesource of energy is limited it becomes of paramount importance to reduce the ohmic resistance of the machine to a minimum. In the .case ofmotor cars the source of energy is a small battery usually consisting ofonly three cells and unless the ohmic resistance of the cranking motorfed by said battery is very small. a sutlicient cranking torque will notbe secured.

It is usual in installations of this kind to ground one terminal of thesource as well as one terminal of the motor.

It has, heretofore. been usual in series motors of the kind referred toto connect all each pole I divide the field windings into as many groupsas there are brush studs of the same polarity and I connect each groupto a diiferent brush stud. Each brush stud may carry one or more brushesas is well understood. v

My invention will be better understood by reference to the accompanyingdrawings in which Fig. 1 is a diagram of my irnproved connections asapplied-to afoucpole motor. Fig. 2 is a cross section through one otitheheld windings and Fig. 3xis a; plan view of two adjacent poles and theirfield windings;

Referring to Fig.1 which illustrates a four pole series motor, thearmature is provided with the commutedrwinding E2 with which co-operatefour brushes, two. of which are positive, while the two others arenegative. Each brush is, of course, carried on a brush stud which,however, is not shown. Each of the four poles carries an excitingwinding (7. 8. S), 10). The winding 7 is grounded at 14L; 8 at 1.3; 9 at16; and 10 at 15. The brushes 3 and 4; are connected to one pole of thebattery 11, the other pole of which. is grounded at 1.2. The positivebrush 5 is connected to the field windings 7, 8 and the brush 6 to thefield windin s 9 and 10.

In order to be able to locate more copper in a given space, I prefer toemploy strip copper for the field windings and to wind it flat, ratherthan on edge. In order to make a ground connection of low resistance Ipreferably provide a slot such as 13 or 14: in the core of each pole,drive the end of the strip which should be grounded into this slot andbraze or solder the copper to the iron. The first couple of turns of thefield winding are entirely insulated in the usual wav. but the rest ofthe turns are bare with independent insulating strips 22 insertedbetween turns. Other insulating strips 23 and 24 are placed between thefield windings and the frame 21 and between the field wind-v ings andthe pole horns. The ends of the adjacent coils which a-rc'not groundedare connected together, for instance as shown at 17 of Fig. 3 and theconnection is so formed as to permit of ready conductive attachment toone of the brush studs.

It was found that this improved winding very considerably increased thetorque of a motor of given dimensions cooperating with a battery ofgiven capacity. In one instance, it was found that the resistance of thefield winding was reduced from .0022 to .0013 of an ohm, while theresistance of the ground connection was reduced from .0014 of an ohm toa value so low that it could not be measured.- The total resistance of amachine provided with a winding as heretofore used, was found to be .0073 of an ohnnwhile the resistance of the same machine when provided withmy improved winding was reduced to .005 ohm. This improvement is in partdue to the better grounding and in part to the fact that my improvedform of winding permits more copper to be located in a given space.lVit-hout change of battery, the current taken by the motor whenstanding still "as raised from e85 to 590 amperes and the torque wasincreased from 4.32 to foot pounds.

Another advantage oil? the arrangement of field. coils shown in Fig. lthat the brush 5 is thereby made to carry exactly the same current asbrush 6. This results in a more equal wear in the two brushes.

Having fully described my invention what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A multipolar direct current motor having a plurality oi? field coilsthe coils of its several poles being connected in parallel in groups,the number of groups corresponding to the number of commutator brushcarriers of like polarity and each group being connected to one of saidbrush carriers.

2. A dynamo electric machine having a plurality of field poles and coilseach field pole core being provided with an opening. and one end of eachfield coil being positioned in the opening; in its pole and electricallyconnected thereto. said coils being of strip conductingmaterial woundflat and said strips being of a width only slightly less than the lengthof the pole core.

In testimony whereof, I have hereunto set my hand and aflixed mv seal.

HANS VVEICHSEL.

